Polycarbonate and polyester blends

ABSTRACT

Disclosed are clear blends comprising: 
     (A) from 1 to 99 percent by weight of a polycarbonate comprising a diol component comprising from 5 to 100 mol percent units of a diphenol or mixture of diphenols having the formula ##STR1## (B) from 1 to 99 percent by weight of a polyester comprising (a) a dicarboxylic acid component comprising from 80 to 100 mol percent 1,4-cyclohexane-dicarboxylic acid units; and from 0 to about 20 mol percent modifying dicarboxylic acid units having from 2 to 20 carbons, and 
     (b) a glycol component comprising from 10 to 75 mol percent 2,2,4,4-tetramethyl-1,3-cyclobutanediol units, from 25 to 90 mol percent 1,4-cyclohexanedimethanol units, and from 0 to 10 mol percent modifying glycol units having 2 to 16 carbons, 
     wherein the total units of said polyester is equal to 200 mol percent; wherein said blend is clear and the total weight percent of said polycarbonate (A) and said polyester (B) is equal to 100 weight percent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional application Ser.No. 60/034,153, filed Dec. 28, 1996, and the application Ser. No.60/034,153 is herein incorporated by this reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to clear blends of polycarbonates andpolyesters. More particularly, the present invention relates to clearblends of polycarbonates of dihydroxydiphenyl cycloalkanes andoptionally bisphenol A with polyesters from 1,4-cyclohexanedicarboxylicacid (trans, cis, or mixtures thereof), 1,4-cyclohexanedimethanol and2,2,4,4-tetramethyl-1,3-cyclobutanediol.

BACKGROUND OF THE INVENTION

The polycarbonate of 4,4'-isopropylidenediphenol (bisphenol Apolycarbonate) is a well known engineering molding plastic. Bisphenol Apolycarbonate is a clear high-performance plastic having good physicalproperties such as dimensional stability, high heat resistance, and goodimpact strength. Although bisphenol A polycarbonate has many goodphysical properties, its relatively high melt viscosity leads to poormelt processability and the polycarbonate exhibits poor chemicalresistance.

Blends of the polycarbonates of bisphenol A and variousdihydroxydiphenyl cycloalkanes have been used in making plastic films,molded articles, and extruded articles. These polycarbonate blends areespecially useful in the performance plastics industry because they tendto have good heat resistance, high melt viscosities suitable forinjection molding and extrusion, toughness, and good chemicalresistance.

U.S. Pat. No. 5,034,457 discloses blends of dihydroxydiphenylcycloalkane polycarbonates with a mixture of amorphous thermoplastics,partly crystalline thermoplastics, and rubber used for injectionmolding. U.S. Pat. No. 5,104,723 discloses blends of dihydroxydiphenylcycloalkane polycarbonates with amorphous thermoplastics, partiallycrystalline thermoplastics, and elastomers for the production of films.

However, there has been no disclosure of miscible blends ofdihydroxydiphenyl cycloalkane polycarbonates with other materials.Immiscible blend compositions are inadequate for many uses because theyare opaque, and generally result in an unacceptable reduction in impactstrength and tensile strength.

Clear, miscible blends of any two polymers are rare. The term "miscible"refers to blends that are a mixture on a molecular level whereinintimate polymer-polymer interaction is achieved. Miscible blends areclear, not translucent or opaque. In addition, differential scanningcalorimetry testing detects only a single glass transition temperature(Tg) for miscible blends composed of two or more components.

There have been very few clear polycarbonate/polyester blends developed.U.S. Pat. Nos. 4,619,976 and 4,645,802 disclose clear blends based onbisphenol A polycarbonate with polyesters of poly(1,4-tetramethyleneterephthalate), poly(1,4-cyclohexylenedimethylene terephthalate) andselected copolyesters and copoly(ester-imides) ofpoly(1,4-cyclohexylenedimethylene terephthalate). U.S. Pat. No.4,786,692 discloses clear blends of bisphenol A polycarbonate andpolyesters of terephthalic acid, isophthalic acid, ethylene glycol, and1,4-cyclohexanedimethanol. U.S. Pat. Nos. 4,188,314 and 4,391,954disclose clear blends of bisphenol A polycarbonate withpoly(1,4-cyclohexylenedimethylene terephthalate-co-isophthalate). Thesepolyester blends do have improved chemical resistance and meltprocessability, when compared to unblended bisphenol A polycarbonate.However, the good heat resistance and impact strength of bisphenol Apolycarbonate blends based on these compositions is reducedsignificantly.

In light of the above, it would be desirable to be able to form clearpolyester blends of dihydroxydiphenyl cycloalkane polycarbonates havinggood melt processability suitable for injection molding. Such blendwould be especially suitable for the manufacture of clear moldedarticles, fibers, sheeting, and film.

SUMMARY OF THE INVENTION

The blend composition according to the present invention comprises:

(A) about 1 to 99 percent by weight of a polycarbonate comprising a diolcomponent comprising about 5 to 100 mol percent units of a diphenol ormixture of diphenols having the formula ##STR2## wherein R₀, R₁, R₂, R₃,R₄, R₅, R₆, and R₇ are independently selected from the group consistingof hydrogen, halogen, C₁ -C₈ alkyl, C₅ -C₁₂ cycloalkyl, C₅ -C₁₂ aryl,and C₆ -C₁₂ aralkyl,

X represents carbon,

m is an integer of from 4 to 7, and

and R₈ and R₉ are independently selected for each X and independentlyselected of each other from the group consisting of hydrogen and C₁ -C₃alkyl;

0 to about 95 mol percent 4,4'-isopropylidenediphenol units, and about 0to about 10 mol percent modifying glycol units having 2 to 16 carbons,wherein the total mol percent of diol units is equal to 100 mol percent;and

(B) about 1 to 99 percent by weight of a polyester comprising

(a) a dicarboxylic acid component comprising about 80 to 100 mol percent1,4-cyclohexanedicarboxylic acid units, and 0 to about 20 mol percentmodifying dicarboxylic acid units having about 2 to 20 carbons, whereinthe total mol percent of dicarboxylic acid units is equal to 100 molpercent; and

(b) a glycol component comprising about 10 to 75 mol percent2,2,4,4-tetramethyl-1,3-cyclobutanediol units, about 25 to 90 molpercent 1,4-cyclohexanedimethanol units, and 0 to about 10 mol percentmodifying glycol units having 2 to 16 carbons, wherein the total molpercent of glycol units is equal to 100 mol percent;

wherein the total units of said polyester is equal to 200 mol percent;wherein said blend is clear and the total weight percent of saidpolycarbonate (A) and said polyester (B) is equal to 100 weight percent.

The invention also covers a method of using the blend compositions toproduce a clear article of manufacture. The method of using the clearblend composition to produce a clear article of manufacture comprisesthe steps of:

(a) blending polycarbonate (A) and polyester (B);

(b) before, during or after the blending, melting polycarbonate (A) andpolyester (B) to form, after the blending and melting, a melt blend;

(c) then cooling the melt blend to form a clear blend composition

DETAILED DESCRIPTION OF THE INVENTION

The present invention may be understood more readily by reference to thefollowing detailed description of preferred embodiments of the inventionand the Examples included therein.

Before the present compositions of matter are disclosed and described,it is to be understood that this invention is not limited to specificsynthetic methods or to particular formulation, as such may, of course,vary. It is also to be understood that the terminology used herein isfor the purpose of describing particular embodiments only and is notintended to be limiting.

In this specification, the singular forms "a", "an" and "the" includeplural referents unless the context clearly dictates otherwise.

The applicants were very surprised to discover clear blends of thepolycarbonate of the diphenol of formula (I) with particular polyestersfrom 1,4-cyclohexanedicarboxylic acid, isophthalic acid,2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 1,4-cyclohexanedimethanol.The applicants were also surprised to discover clear blends ofcopolycarbonates of the diphenol of formula (I) and bisphenol A withparticular polyesters from 1,4-cyclohexanedicarboxylic acid, isophthalicacid, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and1,4-cyclohexanedimethanol.

This discovery was surprising since there are no teachings of clearpolycarbonate/polyester blends based on the polycarbonate of adihydroxydiphenyl cycloalkane. This discovery was particularlysurprising since there are no teachings of a polycarbonate/polyesterblend having a 2,2,4,4-tetramethyl-1,3-cyclobutanediol based glycolcomponent in the polyester. Nor are there any teachings suggesting thatsuch a blend may be clear. Although U.S. Pat. No. 3,301,777 disclosespolyesters containing 2,2,4,4-tetramethyl-1,3-cyclobutanediol, there isno suggestion of the benefit of blending a2,2,4,4-tetramethyl-1,3-cyclobutanediol based polyester with apolycarbonate.

It was further surprising to find that a clear polycarbonate blend isformed with a polyester of 1,4-cyclohexanedimethanol and a substantialamount of 2,2,4,4-tetramethyl-1,3-cyclobutanediol. U.S. Pat. No.4,391,954 discloses that a bisphenol A polycarbonate blend is likely tobe compatible when the glycol component of the polyester is composed of1,4-cyclohexane dimethanol units, with only a minor amount of otherglycol units present. However, the applicants have found that the blendsof the present invention are clear when the polyester has a combinationof 0 to 100 mol percent 1,4-cyclohexane- dimethanol and 0 to 100 molpercent 2,2,4,4-tetramethyl-1,3-cyclobutanediol forming the glycolcomponent. This was found to be true even when the diol component of thepolycarbonate portion of the blend contains, besides bisphenol A units,up to 100 mol percent units of the dihydroxydiphenyl cycloalkane offormula (I).

It was utmost unexpected that a polyester having a dicarboxylic acidcomponent of 1,4-cyclohexane-dicarboxylic acid units, instead of unitsof the much more typically favored aromatic para oriented dicarboxylicacids such as those listed in U.S. Pat. No. 4,391,954, would provide aclear blend which retains much of the mechanical and physical propertiesof the polycarbonate.

There have been no previous suggestions that combining1,4-cyclohexanedimethanol and 2,2,4,4-tetramethyl- 1,3-cyclobutanediolin a polyester would form a clear polycarbonate blend. For example, seeU.S. Pat. No. 3,313,777 and Defensive Publication T-875,010 fordisclosure of polyesters based on 1,4-cyclohexane dimethanol and2,2,4,4-tetramethyl-1,3-cyclobutanediol.

The term "polycarbonate" is herein defined as the condensation productof a carbonate source and a diol source, having a carbonate componentcontaining 100 mol percent carbonate units and a diol componentcontaining 100 mol percent diol units, for a total of 200 mol percentmonomeric units. The term "diol" as used herein, includes both aliphaticand aromatic compounds having two hydroxyl groups, while the term"glycol" refers to aliphatic and aromatic/aliphatic compounds having twohydroxyl groups.

The polycarbonate portion of the blend of the present invention is basedupon the polycarbonate of the diphenol or mixture of diphenols offormula (I). ##STR3## in which R₀, R₁, R₂, R₃, R₄, R₅, R₆, and R₇independently of one another are hydrogen, halogen, C₁ -C₈ alkyl, C₅-C₁₂ cycloalkyl, C₅ -C₁₂ aryl or C₆ -C₁₂ aralkyl, X represents carbon, mis an integer from 4 to 7, and R₈ and R₉ are, independently for each Xand independently of one another, hydrogen or C₁ -C₈ alkyl.

Suitable halogen substituents of the diphenol of formula (I) include,but are not limited to, chlorine, bromine and fluorine. Examples ofsuitable alkyl substituent groups include, but are not limited to,methyl, ethyl, propyl, isopropyl, t-butyl, pentyl, hexyl, heptyl andoctyl. Examples of suitable cycloalkyl substituent groups include, butare not limited to, the cyclohexyl, and the methyl-, ethyl-, propyl-,and t-butyl-cyclohexyl moieties. Examples of suitable aryl substituentgroups include, but are not limited to, phenyl, benzyl, substitutedalkyl phenyl, substituted halophenyl and naphthyl.

The preferred diphenol of formula (I) is a cyclohexyl diphenol shown byformula (II) below, wherein R₀ through R₇ are selected as describedabove. The most preferred diphenol of formula (I) is the condensationproduct of isophorone and phenol known as 3,3,5-trimethylcyclohexanebisphenol, the cyclohexyl diphenol of formula (II) in which R₀ throughR₇ are substituted with hydrogen. ##STR4##

The polycarbonate portion of the blend of the present invention ispreferably a copolycarbonate of the diphenol of formula (I) and4,4'-isopropylidenediphenol, commonly known as bisphenol A, shown belowin formula (III). ##STR5##

Suitable polycarbonates are those having a diol component containingabout 5 to 100 mol percent formula (I) diphenol units and 0 to about 95mol percent bisphenol A units, preferably about 10 to 90 mol percentformula (I) diphenol units and about 10 to 90 mol percent bisphenol Aunits, more preferably about 20 to 50 mol percent formula (I) diphenolunits and about 50 to 80 mol percent bisphenol A units, most preferablyabout 30 to 35 mol percent formula (I) diphenol units and about 65 to 70mol percent bisphenol A units. One especially suitable commercialcopolycarbonate is APEC HT copolycarbonate from Miles, Inc. Theapproximate diol component structure of APEC HT, as determined bynuclear magnetic resonance spectroscopy (NMR), is 68 mol percentbisphenol A units and 32 mol percent 3,3,5-trimethylcyclohexanebisphenol units.

For the polycarbonates of the invention, suitable carbonate sources forthe carbonate units are preferably phosgene, dialkyl carbonate, such aspreferably dibutyl carbonate; or diaryl carbonate, such as preferablydiphenyl carbonate.

Up to 10 mol percent of the diol component of the polycarbonate portioncan be substituted with units of other modifying aromatic diols, besidesbisphenol A and formula (I) diphenol, having from 2 to 16 carbons. It ispreferable to have no more than 5 mol percent of other modifyingpolycarbonate present in the polycarbonate portion of the blend, morepreferably 0 mol percent. The modifying polycarbonates are preferablypolycarbonates of aromatic diols. Suitable examples of other modifyingdiols include the aromatic diols of U.S. Pat. Nos. 3,030,335 and3,317,466.

The inherent viscosity of the polycarbonate portion of the blendsaccording to the present invention is preferably at least about 0.3dL/g, more preferably at least 0.5 dL/g, determined at 25° C. in 60/40wt/wt phenol/tetrachloroethane.

"Polyester," as used herein, refers to any unit-type of polyesterfalling within the scope of the polyester portion of the present blend,including but not limited to homopolyesters, copolyesters, andterpolyesters. The polyester portion of the blend of the presentinvention comprises a dicarboxylic acid component of about 80 to 100 molpercent 1,4-cyclohexanedicarboxylic acid units, and 0 to about 20 molpercent modifying dicarboxylic acid units, and a glycol component ofabout 10 to 75 mol percent 2,2,4,4-tetramethyl-1,3-cyclobutanediolunits, about 25 to 90 mol percent 1,4-cyclohexanedimethanol units, and 0to about 10 mol percent modifying glycol units, wherein the totaldicarboxylic acid units is equal to 100 mol percent, the total glycolunits is equal to 100 mol percent, with a total polyester units equal to200 mol percent.

The 1,4-cyclohexanedicarboxylic acid used to prepare the polyester canbe trans, cis, or mixtures thereof. The 1,4-cyclohexanedicarboxylic acidunits are preferably about 50 to 100 mol percent trans, where the totalof cis and trans isomer content is equal to 100 mol percent, morepreferably the isomer content is greater than about 90 mol percent transisomer. Substantially trans isomer content is preferred because it ismuch more economical to obtain and provides more impact strength to thepolymer.

In addition to 1,4-cyclohexanedicarboxylic acid units the dicarboxylicacid component of the polyester can be substituted with up to 20 molpercent, but preferably less than 10 mol percent of other modifyingdicarboxylic acids having 2 to 20 carbon atoms. Suitable examples ofmodifying aromatic dicarboxylic acids include terephthalic acid,isophthalic acid, 4,4'-biphenyldicarboxylic acid, 1,4-, 1,5-, 2,6-,2,7-naphthalenedicarboxylic acid, 4,4'-oxybenzoic,trans-4,4'-stilbenedicarboxylic acid, or mixtures thereof. Suitableexamples of modifying aliphatic dicarboxylic acids are those containing2 to 12 carbon atoms, such as oxalic, malonic, succinic, glutaric,adipic, pimelic, suberic, azelaic, and sebacic acids, or mixturesthereof.

The dicarboxylic acid component of the polyester portion of the presentblend can be prepared from dicarboxylic acids, their correspondingesters, or mixtures thereof. Examples of esters of the dicarboxylicacids useful in the present invention include the dimethyl, dipropyl,diisopropyl, dibutyl, and diphenyl esters, and the like.

The glycol component of the polyester portion of the present blend isformed from about 10 to 75 mol percent of2,2,4,4-tetramethyl-1,3-cyclobutanediol units and about 25 to 90 molpercent 1,4-cyclohexanedimethanol units, and up to 10 mole percentmodifying glycol units containing 2 to 16 carbons. About 20 to 70 molpercent 2,2,4,4-tetramethyl-1,3-cyclobutanediol units and about 30 to 80mol percent 1,4-cyclohexanedimethanol units preferably form thepolyester glycol component, with about 30 to 50 mol percent2,2,4,4-tetramethyl-1,3-cyclobutanediol units and about 50 to 70 molpercent 1,4-cyclohexanedimethanol units being most preferred.

The 2,2,4,4-tetramethyl-1,3-cyclobutanediol units and the1,4-cyclohexanedimethanol units can be cis, trans, or a mixture thereof.The 2,2,4,4-tetramethyl-1,3-cyclobutanediol units are preferably 45-55mol percent trans, where the total of cis and trans isomer content isequal to 100 mol percent, more preferably the isomer content is about50/50 trans/cis. The 1,4-cyclohexanedimethanol units are preferablyabout 50 to 80 mol percent trans, where the total of cis and transisomer content is equal to 100 mol percent, more preferably about 70/30trans/cis.

The glycol component of the polyester portion of the present blendcontains 0 to about 10 mol percent, but preferably less than 5 molpercent of other modifying glycol units containing 2 to 16 carbon atoms.Examples of suitable modifying glycols include ethylene glycol,1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, p-xylene glycol, and mixtures thereof.The glycol component can also be modified with 0 to about 10 mol percentpolyethylene glycol or polytetramethylene glycols to enhance elastomericbehavior.

The preferred polyester is formed from 1,4-cyclohexanedicarboxylic acidunits having at least 50 mol percent trans isomer content, 20 to 60 molpercent 2,2,4,4-tetramethyl-1,3-cyclobutanediol units, and 40 to 80 molpercent 1,4-cyclohexanedimethanol units with no other modifying glycols.

The blends of the present invention are about 1 to 99 weight percentpolyester portion and about 1 to 99 weight percent polycarbonateportion, with the total weight percent of the polycarbonate portion andpolyester portion preferably being equal to 100 weight percent. Thepreferred blend of the present invention is about 20 to 99 weightpercent polycarbonate and about 1 to 80 weight percent polyester, morepreferably about 40 to 99 weight percent polycarbonate and about 1 to 60weight percent polyester, with a weight percent of about 45 to 55 forboth polycarbonate and polyester being most preferred.

Greater concentrations of the copolycarbonate of the blend nearer 99weight percent produce blends having greater impact strength, heatresistance, and dimensional stability, while blends nearer 99 weightpercent polyester have better chemical resistance and meltprocessability. The most useful blends will be those clear blends havinga combination of physical properties best suited for a particular enduse, as will be determined on a case by case basis.

The inherent viscosity of the polyester portion of the blends accordingto the present invention is preferably at least 0.3 dL/g, morepreferably at least 0.6 dL/g, determined at 25° C. in 60/40 wt/wtphenol/tetrachloroethane.

The blend compositions of the present invention are clear. The term"clear" is defined herein as an absence of cloudiness, haziness, andmuddiness, when inspected visually. The blends of the present inventionalso exhibit a single glass transition temperature (Tg), a s determinedby differential scanning calorimetry DSC).

The chemical resistance and melt processability of the blends of thepresent invention are good. It is generally known that blending with apolyester improves the chemical resistance and melt processability ofpolycarbonates. See U.S. Pat. Nos. 4,188,314 and 4,267,096.

The polycarbonate portion of the present blend can be prepared in themelt, in solution, or by interfacial polymerization techniques wellknown in the art. Suitable methods include the steps of reacting acarbonate source with a diol or diols at a temperature of about 0° C. to315° C. at a pressure of about 0.1 to 760 mm Hg for a time sufficient toform a polycarbonate. Commercially available polycarbonates that aretypically used in the present invention are normally made by reacting anaromatic diol with a carbonate source such as phosgene, dibutylcarbonate or diphenyl carbonate, to incorporate 100 mol percent ofcarbonate units, along with 100 mol percent diol units into thepolycarbonate. For examples of methods of producing polycarbonates, seeU.S. Pat. Nos. 5,498,688, 5,494,992, and 5,489,665 which areincorporated by this reference in their entireties for all of theirteachings.

The polyester portion of the present invention can be made by processesknown from the literature such as, for example, by processes inhomogeneous solution, by transesterification processes in the melt andby two phase interfacial processes. Suitable methods include the stepsof reacting one or more dicarboxylic acids with one or more glycols at atemperature of about 100° C. to 315° C. at a pressure of about 0.1 to760 mm Hg for a time sufficient to form a polyester. See U.S. Pat. No.3,772,405 for methods of producing polyesters.

The polyester/polycarbonate blends of the present invention can be madeby methods which include the steps of blending the polycarbonate andpolyester portions of the present invention at a temperature of about25° C. to 350° C. for a time sufficient to form a clear blendcomposition. Suitable conventional blending techniques include the meltmethod and the solution-prepared method. Other suitable blendingtechniques include dry blending and/or extrusion.

The melt blending method includes blending the polymers at a temperaturesufficient to melt the polycarbonate and polyester portions, andthereafter cooling the blend to a temperature sufficient to produce aclear blend. The term "melt" as used herein includes, but is not limitedto, merely softening the polymers. For melt mixing methods generallyknown in the polymers art, see Mixing and Compounding of Polymers (I.Manas-Zloczower & Z. Tadmor eds., Carl Hanser Verlag publisher, New York1994).

The solution-prepared method includes dissolving the appropriateweight/weight ratio of polyester and polycarbonate in a suitable organicsolvent such as methylene chloride or a 70/30 mixture of methylenechloride and hexafluoroisopropanol, mixing the solution, and separatingthe blend composition from solution by precipitation of the blend or byevaporation of the solvent. Solution-prepared blending methods aregenerally known in the polymers art.

The melt blending method is the preferred method for producing the blendcompositions of the present invention. The melt method is moreeconomical and safer than the solution-prepared method which requiresthe use of volatile solvents. The melt method is also much moreeffective in providing clear blends. Any of the clear blends of thepresent invention that can be prepared by solution blending can also beprepared by the melt method. However, some of the blends of the presentinvention can be prepared by the melt method, but not by the solutionmethod. Any blending process which provides clear blends of the presentinvention is suitable. One of ordinary skill in the art will be able todetermine appropriate blending methods for producing the clear blends ofthe present invention.

In addition to the polycarbonate and polyester portions disclosed above,the blend of the present invention can include at least one othermodifying polymer. Suitable modifying polymers are those which formmiscible blends with the polycarbonate and polyester portions disclosedabove. Possible modifying polymers include other polycarbonates, otherpolyesters, polyamides, polystyrenes, polyurethanes, polyarylates,liquid crystalline polymers, vinyl polymers, and the like, or a mixturethereof. Suitable modifying polymers may be determined by one ofordinary skill in the polymers art by performing traditional miscibilitytests with possible modifying polymers.

A polymer may be determined to be a suitable modifying polymer of theblend of the present invention if a clear blend is formed by: 1)blending the modifying polymer with a pre-existing blend containing thepolycarbonate and polyester portions, or 2) blending the modifyingpolymer with the polycarbonate portion prior to the introduction of thepolyester portion, or 3) blending the modifying polymer with thepolyester portion prior to the introduction of the polycarbonateportion, or 4) mixing the modifying polymer, polycarbonate portion andpolyester portion all together prior to blending.

The clear blends of the present invention can still be further modifiedby the incorporation of blend modifiers to produce performance blendswhich may not necessarily be clear. For example, polyamides such asnylon 6,6 from DuPont, poly(ether-imides) such as ULTEMpoly(ether-imide) from General Electric, polyphenylene oxides such aspoly(2,6-dimethylphenylene oxide) or poly(phenylene oxide)/polystyreneblends such as the NORYL resins from General Electric, polyesters,polyphenylene sulfides, polyphenylene sulfide/sulfones,poly(ester-carbonates) such as LEXAN 3250 poly(ester-carbonate) (GeneralElectric), polycarbonates other than LEXAN polycarbonate from GeneralElectric, polyarylates such as ARDEL D100 polyarylate (Amoco),polysulfones, polysulfone ethers, poly(ether-ketones) or aromaticdihydroxy compounds can be used as blend modifiers to modify propertiesor to reduce flammability. The aromatic dihydroxy compounds used toprepare these polymers are disclosed in U.S. Pat. No. 3,030,335 and U.S.Pat. No. 3,317,466.

The blends of the present invention can also contain antioxidants,conventional flame retardants such as phosphorus or halogen compounds,or fillers such as talc or mica, or reinforcing agents such as glassfiber, KEVLAR, or carbon fiber. Additives such as pigments, dyes,stabilizers, plasticizers, etc. can also be used in the polyesters,polycarbonates, and blends of the present invention to further modifythe properties of the inventive blends.

The blends of the present invention are useful in producing cleararticles of manufacture having improved chemical resistance and meltprocessability while retaining excellent mechanical properties. Theseblends are especially useful for making molded articles, fibers, films,and sheeting.

The following examples are intended to illustrate the present inventionbut are not intended to limit the reasonable scope thereof.

EXAMPLES

The inherent viscosity of the polyesters was determined in 60/40 (wt/wt)phenol/tetrachloroethane at a concentration of 0.5 g/100 mL at 25° C.The glass transition temperatures (Tg's) were determined using a DuPont912 DSC (differential scanning calorimeter) at a scan rate of 20°C./min. The glycol content of the polyester portion of these blends wasdetermined by proton nuclear magnetic resonance spectroscopy (NMR).Clarity was determined visually. The miscibility of the blends wasdetermined by differential scanning calorimetry and by observation ofthe clarity of polymer/polymer melts or pressed films.

The blends of this invention were prepared in two ways:

1) The solution-prepared method of dissolving the appropriateweight/weight ratio of polyester to polycarbonate in methylene chlorideor a mixture of methylene chloride/hexafluoroisopropanol and aftercomplete solution was obtained, precipitating the blend with methanol.

2) The melt mixing method of dry blending the appropriate weight/weightratio of polyester to polycarbonate and extruding the blend on a 3/4-inBrabender extruder equipped with a screen pack and mixing screw attemperatures of 260-320° C.

The preparation of polycarbonates is well known in the art. Thepolycarbonate used in the following examples was APEC HT copolycarbonatefrom Miles, Inc. The bisphenol A polycarbonate used was MAKROLON 2608,available from Miles, Inc.

The following examples illustrate the preparation of some of thepolyesters used in this invention and their miscibility with APEC HTpolycarbonate.

Example 1

Examples 1A-1K illustrate the miscibility of 50/50 wt/wtsolution-prepared blends of APEC HT copolycarbonate and a copolyestercontaining 100 mol percent 1,4-cyclohexanedicarboxylic acid units andvarying amounts of 2,2,4,4-tetramethyl-1,3-cyclobutanediol units and1,4-cyclohexanedimethanol units. Examples 1A-1K were all prepared in asimilar manner. The specific preparation of the polyester and blend forExample 1G and Example 1K (Control) are shown below. The results arepresented in Table 1.

Example 1G illustrates the preparation of a clear blend obtained fromblending APEC HT copolycarbonate with a copolyester prepared from 100mol percent dimethyl trans-1,4-cyclohexanedicarboxylate, 60 mol percent2,2,4,4-tetramethyl-1,3-cyclobutanediol (50/50 trans/cis), and 40 molpercent 1,4-cyclohexanedimethanol (70/30 trans/cis).

To prepare the copolyester for Example 1G, a mixture of 120.0 g (0.60mol) dimethyl trans-1,4-cyclohexanedicarboxylate, 47.3 g (0.22 mol)1,4-cyclohexanedimethanol (70/30 trans/cis) (67% in methanol), 56.2 g(0.39 mol) 2,2,4,4-tetramethyl-1,3-cyclobutanediol (50/50 trans/cis),0.168 g IRGANOX 1010 (an antioxidant by Ciba-Geigy), 0.10 g titaniumtetraisopropoxide (100 ppm Ti), and 0.14 g dibutyltin oxide (400 ppm Sn)was placed in a 1-L flask equipped with an inlet for argon, a metalstirrer, and a short distillation column. The flask was placed in aBelmont metal bath already heated to 220° C. and the contents of theflask were heated at 220° C. for 6 hours. The temperature was raised to250° C. After the temperature reached 250° C., a vacuum of 0.5 mmmercury was gradually applied over the next 3-5 minutes. Full vacuum wasmaintained for a total time of about 3 hours. A high melt viscosity,light yellow polymer was obtained with a glass transition temperature of99° C. and an inherent viscosity of 0.65 dL/g.

The polyester was then ground to pass a 3-mm screen and 0.25 g of thepolyester was dissolved in methylene chloride with 0.25 g APEC HTcopolycarbonate. After solution was complete, the polymers wereprecipitated by dropping the blend solution into methanol. Theprecipitate which formed was collected, dried in a vacuum oven for 72hours at 50° C., and determined to have a single glass transitiontemperature.

The blend was thereafter melted and pressed into a thin film. The filmappeared visually clear.

Example 1K (Control) illustrates the preparation of the1,4-cyclohexanedicarboxylic/2,2,4,4-tetramethyl-1,3-cyclobutanediolhomopolyester and the preparation of a 50/50 weight percent APEC HTcopolyester blend.

To prepare the homopolyester for Example 1K, a mixture of 100.0 g (0.500mol dimethyl 1,4-cyclohexanedicarboxylate, 75.6 g (0.525 mol)2,2,4,4-tetramethyl-1,3-cyclobutanediol (50/50 trans/cis), 0.10 gtitanium tetraisopropoxide (125 ppm Ti), 0.15 g dibutyltin oxide (500ppm Sn), and 0.125 g IRGANOX 1010 was placed in a 1-L flask equippedwith an inlet for argon, a metal stirrer, and a short distillationcolumn. The flask was placed in a Belmont metal bath already heated to220° C. The contents of the flask were heated at 220° C. for 5.5 hours.The temperature was raised to 250° C. After the temperature reached 250°C., a vacuum of 0.5 mm was gradually applied over the next 3-5 minutes.Full vacuum was maintained for 1 hour at 250° C. and 1 hour at 260° C. Ahigh melt viscosity, clear polymer was obtained with a glass transitiontemperature of 121° C. and an inherent viscosity of 0.37 dL/g.

The polyester was ground to pass a 3-mm screen and 0.25 g of thepolyester was dissolved in methylene chloride-with 0.25 g APEC HTcopolycarbonate. After solution was complete, the polymers wereprecipitated by dropping the blend solution into methanol. Theprecipitate was collected, dried in a vacuum oven for 72 hours at 50°C., and determined to have two glass transition temperatures. The blendwas melted and pressed into a thin film. The film appeared opaque.

It can be seen from Table 1 that Examples 1B-1H, the blends containingbetween 10 to 70 mol percent 2,2,4,4-tetramethyl-1,3-cyclobutanediolunits, with the remaining glycol units being 1,4-cyclohexanedimethanolunits, were unexpectedly clear, even when using the less preferredsolution blending method.

                  TABLE 1                                                         ______________________________________                                        Solution Prepared Blends of Polyesters of 1,4-Cyclohexanedicarboxylic         acid 2,2,4,4-Tetramethyl-1,3-cyclobutanediol, and                             1,4-Cyclohexanedimethanol with APEC HT Copolycarbonate                        Blend Composition: 50 wt. % Polycarbonate/50 wt. % Polyester                  Ex-   Polyester Composition                                                                           Blend Visual                                                                            DSC                                         ample CHDM, Mol %                                                                              TMCD, Mol %                                                                              Clarity Number of Tgs                             ______________________________________                                        1A    100         0         Cloudy  Two                                       1B    90         10         Clear   --                                        1C    80         20         Clear   --                                        1D    70         30         Clear   One                                       1E    60         40         CIear   One                                       1F    50         50         Clear   One                                       1G    40         60         Clear   One                                       1H    30         70         Clear   One                                       1I    20         80         Cloudy  Two                                       1J    10         90         Cloudy  Two                                       1K     0         100        Opaque  Two                                       ______________________________________                                         1,4-cyclohexanedicarboxylic acid (99/1 trans/cis)                             TMCD = 2,2,4,4tetramethyl-1,3-cyclobutanediol (50/50 trans/cis),              CHDM = 1,4cyclohexane dimethanol (70/30 trans/cis).                      

Example 2

The blends in this example were prepared by the same solvent blendingmethod used in Example 1. However, the polycarbonate used was abisphenol A polycarbonate, MAKROLON 2608. The results are presented inTable 2. Examples 2C through 2G show results from the same polyesters aswere used in Examples 1C through 1G, respectively. However, the filmswhich were prepared from blends with APEC HT copolyester in Examples 1Cthrough 1G were clear, while the films which were prepared from blendswith bisphenol A polycarbonate in Examples 2C through 2G were cloudy oropaque.

These results demonstrate the importance of the polycarbonate structurein achieving visually clear films.

                  TABLE 2                                                         ______________________________________                                        Solution Prepared Blends of Polyesters of                                     1,4-Cyclohexanedicarboxylic acid,                                             2,2,4,4-Tetramethyl-1,3-cyclobutanediol, and                                  1,4-Cyclohexanedimethanol with Bisphenol A Polycarbonate                      Blend Composition: 50 wt. % Polycarbonate/50 wt. % Polyester                  Example                                                                              CHDM, mol %                                                                              TMCD, mol %                                                                              Clarity                                                                             Number of Tg's                             ______________________________________                                        2A     100         0         Clear One                                        2B     90         10         Clear One                                        2C     80         20         Cloudy                                                                              --                                         2D     70         30         Cloudy                                                                              --                                         2E     60         40         Opaque                                                                              Two                                        2F     50         50         Opaque                                                                              Two                                        2G     40         60         Opaque                                                                              Two                                        2H     30         70         --    --                                         21     20         80         Opaque                                                                              Two                                        2J     10         90         Opaque                                                                              Two                                        2K      0         100        Opaque                                                                              Two                                        ______________________________________                                         1,4-cyclohexanedicarboxylic acid (99/1 trans/cis)                             TMCD = 2,2,4,4tetramethyl-1,3-cyclobutanediol (50/50 trans/cis),              CHDM = 1,4cyclohexane dimethanol (70/30 trans/cis).                      

Example 3

The blends of this example were prepared by melt mixing. Blends of APECHT copolycarbonate with homopolyesters were prepared by an extruder inthe melt. The blend compositions were 50 weight percent polycarbonateand 50 weight percent polyester. The pellets Were first mixed bytumbling. The blends were prepared in a 3/4-in Brabender single screwextruder with a mixing screw. Injection molded parts were prepared on aBoy 22S injection molding machine. Processing temperatures used were inthe range of 280° C. to 315° C. Visual inspection was used to determineclarity.

Example 3A was a blend of 50 weight percent APEC HT copolycarbonate and50 weight percent homopolyester of 1,4-cyclohexanedicarboxylic acid(99/1 trans/cis) and 1,4-cyclohexanedimethanol (70/30 trans/cis).Example 3A exhibited unexpected visual clarity. Note that the clearblend of Example 3A (melt blended) had the same composition as thecloudy, solution blended Example 1A. This difference is believed to bedue to the more intensive mixing which is achieved in the melt.

Example 3B was a blend of 50 weight percent APEC HT copolycarbonate and50 weight percent homopolyester of 1,4-cyclohexanedicarboxylic acid(99/1 trans/cis) and 2,2,4,4-tetramethyl-1,3-cyclobutanediol (50/50trans/cis). Example 3B was opaque and is not part of the presentinvention.

This example illustrates that the melt method is the preferred method ofmaking the blends of the present invention and that while the blends ofthe present invention may be cloudy or opaque when prepared by solutionmethods, they are clear when prepared by melt mixing. Also see thecomparison in melt mixing and solution blending in the copendingapplication for docket 68379, incorporated herein.

Selected mechanical properties of the blend of Example 3A prepared inthe melt were analyzed. Example 3A exhibited a useful combination ofclarity, high heat deflection temperature, and impact strength. The heatdeflection temperature was 95° C. at 66 psi loading, and 85° C. at 264psi loading, as determined according to ASTM D648. The Notched IzodImpact strength determined at 23° C. according to ASTM D256 was 1.1ft-lb/inch. The flexural modulus and flexural strength, determinedaccording to ASTM D790, were 278,000 psi and 11,940 psi, respectively.

As will be apparent to anyone skilled in the art, these compositionshave broad applications including the fabrication of molded articles,fibers, sheeting, or films, particularly where visual clarity isimportant.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modification can be effected within the spirit and scope of theinvention. Moreover, all patents, patent application (published andunpublished, foreign or domestic), literature references or otherpublications noted above are incorporated herein by reference for anydisclosure pertinent to the practice of this invention.

We claim:
 1. A blend composition comprising:(A) from 1 to 99 percent by weight of a polycarbonate comprising a diol component comprising from 5 to 100 mol percent units of a diphenol or mixture of diphenols having the formula ##STR6## wherein R₀, R₁, R₂, R₃, R₄, R₅, R₆, and R₇ are independently selected from the group consisting of hydrogen, halogen, C₁ -C₈ alkyl, C₅ -C₁₂ cycloalkyl,C₅ -C₁₂ aryl, and C₆ -C₁₂ aralkyl, X represents carbon, m is an integer of from 4 to 7, and R₈ and R₉ are independently selected for each X and independently selected of each other from the group consisting of hydrogen and C₁ -C₈ alkyl; 0to about 95 mol percent 4,4'-isopropylidenediphenol units, and about 0 to about 10 mol percent modifying glycol units having 2 to 16 carbons, wherein the total mol percent of diol units is equal to 100 mol percent; and (B) from 1 to 99 percent by weight of a polyester comprising(a) a dicarboxylic acid component comprising from 80 to 100 mol percent 1,4-cyclohexane-dicarboxylic acid units; and from 0 to about 20 mol percent modifying dicarboxylic acid units having from 2 to 20 carbons, wherein the total mol percent of dicarboxylic acid units is equal to 100 mol percent; and (b) a glycol component comprising from 10 to 75 mol percent 2,2,4,4-tetramethyl-1,3-cyclobutanediol units, from 25 to 90 mol percent 1,4-cyclohexanedimethanol units, and from 0 to 10 mol percent modifying glycol units having 2 to 16 carbons, wherein the total mol percent of glycol units is equal to 100 mol percent;wherein the total units of said polyester is equal to 200 mol percent; wherein said blend is clear and the total weight percent of said polycarbonate (A) and said polyester (B) is equal to 100 weight percent.
 2. The composition of claim 1 wherein said polycarbonate (A) is present at from 40 to 99 weight percent, based on the weight of the blend composition, and said polyester (B) is present at from 1 to 60 weight percent, based on the weight of the blend composition.
 3. The composition of claim 1, wherein said polycarbonate (A) is present at from 45 to 55 weight percent, based on the weight of the blend composition, and said polyester is present at from 45 to 55 weight percent, based on the weight of the blend composition.
 4. The composition of claim 1 wherein said diol component of said polycarbonate contains from 10 to 90 mol percent diphenol (I) units and from 10 to 90 mol percent 4,4'-isopropylidenediphenol units.
 5. The composition of claim 4 wherein said diol component contains from 20 to 50 mol percent diphenol (I) units and from 50 to 80 mol percent 4,4'-isopropylidenediphenol units.
 6. The composition of claim 4 wherein said diol component contains from 30 to 35 mol percent diphenol (I) units and from 65 to 70 mol percent 4,4'-isopropylidenediphenol units.
 7. The composition of claim 1 wherein said dicarboxylic acid component of said polyester portion contains 100 mol percent 1,4-cyclohexanedicarboxylic acid units.
 8. The composition of claim 1 wherein said 1,4-cyclohexanedicarboxylic acid units are from 50 to 100 mol percent trans, wherein the total of cis and trans isomer content is equal to 100 mol percent.
 9. The composition of claim 8, wherein the 1,4-cyclohexanedicarboxylic acid units are 90 mol percent trans.
 10. The composition of claim 1 wherein said glycol component of said polyester consists essentially of 2,2,4,4-tetramethyl-1,3-cyclobutanediol units and 1,4-cyclohexanedimethanol units.
 11. The composition of claim 1, wherein the 2,2,4,4-tetramethyl-1,3-cyclobutanediol consists of 50 percent cis isomers and 50 percent trans isomer, where the total of the cis and trans isomer is equal to 100 mol percent.
 12. The composition of claim 1 wherein said glycol component of said polyester is from 20 to 70 mol percent 2,2,4,4-tetramethyl-1,3-cyclobutanediol units and from 30 to 80 mol percent 1,4-cyclohexanedimethanol units.
 13. The composition of claim 11 wherein said glycol component of said polyester is from 30 to 50 mol percent 2,2,4,4-tetramethyl-1,3-cyclobutanediol units and from 50 to 70 mol percent 1,4-cyclohexanedimethanol units.
 14. The composition of claim 1 wherein said modifying dicarboxylic acid units of said polyester are selected from the group consisting of terephthalic acid, isophthalic acid, 4,4'-biphenyldicarboxylic acid; 1,4-, 1,5-, 2,6-, 2,7-naphthalenedicarboxylic acid; 4,4'-oxydibenzoic acid; trans-4,4'-stilbenedicarboxylic acid; oxalic acid; malonic acid; succinic acid; glutaric acid; adipic acid; pimelic acid; suberic acid; azelaic acid; sebacic acid; and mixtures thereof.
 15. The composition of claim 1 wherein said modifying glycol units of said polyester are selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, p-xylene glycol, and mixtures thereof.
 16. The composition of claim 1, wherein the polyester consists essentially of cyclohexanedicarboxylic acid units having at least 50 mol percent trans isomer content, from 20 to 60 mol percent 2,2,4,4-tetramethyl-1,3-cyclobutanediol units, and from 40 to 80 mol percent 1,4-cyclohexanedimethanol units.
 17. The composition of claim 1 wherein said diphenol of formula (I) is a cyclohexyl diphenol having the formula ##STR7## wherein R₀, R₁, R₂, R₃, R₄, R₅, R₆, and R₇ are independently selected from the group consisting of hydrogen, halogen, C₁ -C₈ alkyl, C₅ -C₁₂ cycloalkyl, C₅ -C₁₂ aryl, and C₆ -C₁₂ aralkyl.
 18. The composition of claim 17 wherein said cyclohexyl diphenol is 3,3,5-trimethylcyclohexane bisphenol.
 19. The composition of claim 1 wherein said blend composition has a single glass transition temperature.
 20. The composition of claim 1 wherein said polycarbonate has an inherent viscosity of at least 0.3 dL/g at 25° C. and said polyester has an inherent viscosity of at least 0.3 dL/g at 25° C.
 21. A clear article of manufacture made from the composition according to claim 1, selected from the group consisting of molded articles, fibers, films, and sheeting.
 22. A clear article of manufacture made from the composition according to claim
 1. 23. A method of using the blend of claim 1 to produce a clear article of manufacture comprising:(a) blending polycarbonate (A) and polyester (B) of claim 1; (b) before, during or after the blending, melting polycarbonate (A) and polyester (B) to form, after the blending and melting, a melt blend; (c) then cooling the melt blend to form a clear blend composition. 